It is the practice when a draft of a paper or other document is being read or edited and it is desired to make note of a passage of interest or of necessary revisions, to enter the note or change thereon in red pencil or in ink. Where the document is of a nature such that the marking or note has to be removable, it is lightly penciled in so that it can be erased. If the penciling is done too lightly, a loss of legibility may result; if it is entered too darkly, there is a risk that complete erasure is not possible or that the erasing itself can cause damage. It is thus the practice to use removable markers or signals of various kinds to point out, note, or emphasize matter of interest in a paper or other document.